Marketable Securities - Summary of Available-for-sale Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Marketable securities with unrecognized gains	$ 30
Cost
Debt Securities, Available-for-sale [Line Items]
Total available-for-sale securities	14,170	$ 39,033
Cost \| Certificates of deposit \| Level 1
Debt Securities, Available-for-sale [Line Items]
Marketable securities with unrecognized losses for less than 12 months	0	251
Marketable securities with unrecognized gains	1,799	1,799
Total available-for-sale securities	1,799	2,050
Cost \| U.S. Treasury and agency notes \| Level 2
Debt Securities, Available-for-sale [Line Items]
Marketable securities with unrecognized losses for less than 12 months	0	6,485
Marketable securities with unrecognized gains	5,347	14,413
Total available-for-sale securities	5,347	20,898
Cost \| Corporate notes \| Level 2
Debt Securities, Available-for-sale [Line Items]
Marketable securities with unrecognized losses for less than 12 months	1,113	1,004
Marketable securities with unrecognized gains	3,912	13,082
Total available-for-sale securities	5,025	14,086
Cost \| Municipal notes \| Level 2
Debt Securities, Available-for-sale [Line Items]
Marketable securities with unrecognized gains	1,999	1,999
Total available-for-sale securities	1,999	1,999
Fair Value
Debt Securities, Available-for-sale [Line Items]
Total available-for-sale securities	14,199	39,084
Fair Value \| Certificates of deposit \| Level 1
Debt Securities, Available-for-sale [Line Items]
Marketable securities with unrecognized losses for less than 12 months	0	250
Marketable securities with unrecognized gains	1,806	1,806
Total available-for-sale securities	1,806	2,056
Fair Value \| U.S. Treasury and agency notes \| Level 2
Debt Securities, Available-for-sale [Line Items]
Marketable securities with unrecognized losses for less than 12 months	0	6,479
Marketable securities with unrecognized gains	5,360	14,434
Total available-for-sale securities	5,360	20,913
Fair Value \| Corporate notes \| Level 2
Debt Securities, Available-for-sale [Line Items]
Marketable securities with unrecognized losses for less than 12 months	1,112	1,002
Marketable securities with unrecognized gains	3,920	13,106
Total available-for-sale securities	5,032	14,108
Fair Value \| Municipal notes \| Level 2
Debt Securities, Available-for-sale [Line Items]
Marketable securities with unrecognized gains	2,001	2,007
Total available-for-sale securities	$ 2,001	$ 2,007

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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-Section 50
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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 210
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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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